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Abstract
Four sets of bearings were tested on a three-mass overhung flexible rotor: axial-groove, pressure-dam, and two sets of preloaded (0.75 and 0.40) multilobe bearings. The first and second critical speeds were observed at 3200 and 6800 rpm; predicted values were 2960 and 7420, respectively. The instability thresholds were observed to depend strongly on the load orientations for the axial-groove and multilobe bearing. The maximum instability thresholds (optimum load direction for the axial-groove, multilobe (m = 0.75), and multilobe (m = 0.40) bearings were 6700 rpm, 9200 rpm, and 6800 rpm, respectively. For the pressure-dam bearings, it was 6400 rpm and was predicted to be 5800 rpm. The lowest instability threshold for the axial-groove and multilobe bearings were 5750 rpm, 7600 rpm, and 6200 rpm, respectively. When known unbalances were added to the rotor in the pressure-dam bearings, the stability threshold was increased to above the safe running range of the rotor and a brief instability was observed as the rotor traversed the second critical speed. Temporary low level instabilities were also observed for the axial-groove and multilobe (m = 0.40) bearing as the rotor accelerated through approximately twice the first critical speed range.
Presented at the 41st Annual Meeting in Toronto, Ontario, Canada May 12–15, 1986
Notes
Presented at the 41st Annual Meeting in Toronto, Ontario, Canada May 12–15, 1986